#define _CRT_SECURE_NO_WARNINGS 1

class Solution
{
public:
	int peakIndexInMountainArray(vector<int>& arr)
	{
		int left = 1, right = arr.size() - 2;
		while (left < right)
		{
			int mid = left + (right - left + 1) / 2;
			if (arr[mid] > arr[mid - 1]) left = mid;
			else right = mid - 1;
		}
		return left;
	}
};